Electric switching protective system



Feb. 17, 1942. E AN ER 2,273,311

NVENTOR, ERNEST G. HNGER Feb. 17, 1942. ANGER I 2,273,311

ELECTRIC SWITCHING PROTECTIVE SYSTEM Filed April 25, 1958 3 Sheets-Sheet 2 1N VENTOR smvssr a. n/vaa Feb. 17 1942. E, A GER 2,273,311

ELECTRIC SWITCHING PROTECTIVE SYSTEM Filed April 25, 1938 v 3 Sheets-Sheet 3 51 :2 1 Mg! 5: V I

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4? k 42 42 HA1 f g 44/ 44 oovozrir E #7 r .-N!/'ENTOR ERNEST G. HNGER Patented Feb. 17, 1942 ELECTRIC SWITCHING PROTECTIVE SYSTEM 1 Ernest G. Anger, Wauwatosa, Wis, assignor to Square D Company, Detroit, Mich, a. corporation of Michigan Application April 25, 1938, Serial No. 204,052

20 Claims.

This invention relates to an electric circuit controlling device and has for its main object an electric circuit controlling device or switch having provision for ensuring the opening of the circuit at a definite pointwith respect to a reference voltage or current wave.

In the use of electric switches, whether operated electromagnetically or otherwise, it is frequently necessary that the circuit there-' through be timed quite accurately, and the addition of an extra half cycle of current supplied might be such a large percentage of error as to prevent the desired result being accomplished. Should the circuit through the switch or contactor be opened after the alternating current has started to build up from its zero value, the current W111 not be interrupted even though the contacts separate, but the current will continue to flow with arcing at the contact tips until it again approaches an instantaneous value of zero. From this, it follows that a very small difference in timing as to the opening of contacts before or after the current passes through its instantaneous zero value will mean a full half cycle error'in the period during which current is passed to the load circuit; It therefore becomes highly desirable, where accuracy of timing duration of current flow is necessary, that the point with respect to current wave at which the contacts separate be determined.

Furthermore, this arcing at the contact tips, regardless of whether or not accuracy of timing is necessary, is highly undesirable, as it results in a very rapid burning or wearing away of the contact material which necessitates frequent replacement so that the maintenance cost is quite high. Also, such arcing provides very undesirable heating of the contacts and associated parts, and possible burning, with destruction of dielectric and the possibility of breakdown. Further, the maximum interrupting capacity of the switch will be determined by its ability to successiully withstand and interrupt the arcs, thus formed, without breakdown and, accordingly, the interruption of a circuit under its worst possible condition with maximum arcing will determine the interrupting capacity of an ordinary switch.

The electric circuit controlling device or switch, according to the present invention, provides, by very simple and inexpensive apparatus, means whereby not only can any particular point on the reference voltage or current wave be selected at which the contacts separate to interrupt the circuit, but also enables this point to be selected at, or very close to, the instantaneous zero point of the current, so that not only is accuracy of timing ensured but together therewith or entirely separate and distinct therefrom the interruption of the circuit is effected with aminimum of arcing with consequent increased capacity for the switch and the elimination of contact burning and wear.

It is, therefore, one object of the present invention to provide an electric switch having means ensuring the opening of the circuit therethrough at a definite predetermined point on a reference voltage or current wave.

Another object of the invention is the provision of an electric switch having means ensuring the opening of the circuit therethrough when the instantaneous value of the current is substantially zero.

Another object of the invention is an electric switch in which, regardless of the point at which the main operating means is actuated to initiate opening of the switch, the contacts will not separate except at a definite predetermined point with respect to a reference voltage or current wave,

Another object of the invention is an electric switch having main operating means and auX-= iliary holding means which, when the main operating means is actuated. to open the switch, will not release the switch for actual opening movement until a definite point on a reference voltage or current wave is reached.

Another object of the invention is an electric switch having main operating means and an auxiliary electromagnetic holding coil which, regardless of the point at which the main operating means is actuated to effect opening of the switch, will not release the switch for opening movement except when the flux produced by the auxiliary holding. coil has an instantaneous value of substantially zero.

Another object of the invention is an electric switch having a main operating means and an auxiliary electromagnetic holding coil energized from the supply circuit and having sufficient strength to hold the switch closed until the flux produced thereby has an instantaneous value of substantially zero.

Another object of the invention is an electro magnetically operated electric switch having a stationary magnetic circuit and an armature cooperating therewith to produce the normal switching function and a main operating coil about the magnetic circuit with an auxiliary coil adjacent one of the cooperating pole faces on tion,

said armature and magnetic circuit which auxiliary coil is energized from the supply and produce a localized fiux sufficient in strength to hold Que armature in place until the instantaneous yalue of the auxiliary flux approaches the zero after the main operating coil is opened. with the auxiliary fiux too weak to effect return of the released armature as the flux increases in value in the opposite direction.

Other objects and features of the invention will be readily apparent to those skilled in the art fromthe following specification and the appended drawings illustrating certain preferred embodiments of the invention in which:

Figure 1 is a front elevational view of an electromagnetically operated electric switch according to the present invention.

Figure 2 is a side elevational view of the switch shown in Figure 1.

Figure 3 is an enlarged detailed view of the cooperating armature and field magnet pole faces at which the auxiliary coil is disposed.

Figure 4 is a schematic diagram of the wiring arrangement of a switch, according to the present invention, operatively connected to supply a load circuit.

Figure 5 is a simplified vector diagram illustrating the phase relations between the various factors leading to the synchronization of the switch.

Figure 6 is a schematic diagram similar to Figure 4 illustrating an alternative method of energizing the auxiliary coil.

Figure 7 is a graph showing typical holding curves for the operating and auxiliary coils of an electromagnetic contactor.

Figure 8 is a schematic diagram illustrating one manner in which two contactors may be synchronized when connected in series.

The construction of the main operating elements of an electric switch, according to the present invention, may take almost any form. It may be mechanically or otherwise operated and the switching elements may be of any desired construction, elements are readily adaptable for incorporation into any switch which is biased to its open posias distinguished from a positive connection wherein the switching parts would be positively operated by the actuating or operating means.

The specific switch illustrated in the drawings comprises a supporting plate I having mounted on its front face a stationary contact supporting Post 2 as by means of a stud 2. The stationary contact 4 is removably mounted upon a holder 5 adjustably and releasably supported upon the post 2 by means of a stud 8. Spacing shims 1 are provided between the holder 5 and post 2 for adlusting the position of the stationary contact I with respect to the supporting plate I. Above the stationary contact supporting assembly is supported a C-shaped magnet I supported upon the plate I by a pair of brackets I at opposite sides of the stationary contact. Around the magnet I is disposed a blowout coil II having one and connected to the contact post 2 and its opposite end connected to a terminal I2 to which a terminal lug I2 may be attached. A bracket ID as applicant's synchronizing is rigidly mounted on the panel I and receives in supporting relation a pin 'Il rigid with an insulating arc chute II having its lower portion disposed about the stationary contact I and the movable contact cooperating therewith. A pair of angle brackets II are rigidly secured in the opposite sides of the arc chute I5 and are attached to the brackets 9 by the studs I I. The bracket III and pin I 4 and the brackets I5 combine to support the arc chute I5 in its operative position.

Rigidly supported upon the panel i below the contact post 2 is a U -shaped stationary field magnet I8 having wrapped about its upper leg the main operating coil I9. Below the field magnet I8 there is rigidly mounted upon the panel I a supporting bracket structure 2I having at its front face a V-shaped notch 20 providing a bearing for a pivoted operating member 22 which has mounted thereon a magnetic armature member 23. On the front face of the pivoted operating member 22 is rigidly secured a generally U-shaped spring bracket and contact finger guide 24 having disposed between its legs the contact finger 25 and a compression spring 26 bearing against the contact finger and providing the resilient contact pressure in the on position of the switch. A stud 21. is provided for adjusting the tension of the spring 28 for a purpose to be hereinafter described. The contact finger 25 is pivotally mounted on operating member 22 as at ll and in the on position of Figure 2 the operating member 22 is moved to the right with respect to the finger so that in the separating movement of the contact the member 22 will have an appreciable movement toward the left before it rigidly engages the contact finger and moves it to its "off position. Rigidly supported on the panel I are stop posts 28 having a stop 29 mounted thereon for determining the de-energized extreme position of the moving parts. A movable contact 3i is removably mounted on the upper end of the finger 25 in position to cooperate with the stationary contact 4 within the arc chute II. A bracket 32 is rigidly mounted upon the bottom leg of the operating member 22 and a pair of fixed posts 33 have compression springs 24 thereabout which bias the member 22 to its extreme de-energized position. A flexible conductor I interconnects the contact finger 25 with the lower terminal 36 on the panel having connected thereto the terminal lug 21 for reception of the circuit conductor.

The auxiliary holding coil, according to the present invention, is represented in the drawings as a single turn of the wires 38 which is disposed in a pair of horizontal transverse milled slots in the front of the upper pole face of the field magnet l8. A pair of angle members 22 have their shorter legs rigidly connected to the posts 28 and their free ends extended at opposite sides of the pole face and bear against the turn formed by the conductor. 38 to maintain it in place within the slots. This pole face construction is more particularly shown in the enlarged detailed view of Figure 3. It is, of course, understood that while the turn has been illustrated as being located in the stationary pole face, since it is easier to thus connect it to a stationary part, insofar as the working of the invention is concemed it could be connected in the armature pole face, although here, due to the moving part, fiexible connections or some other means connecting the coil into its auxiliary circuit would have to be provided. The conductors 38 forming the auxiliary coil or turn are fed from the secondary of a transformer 4| and a limiting resistor 42 is included in series therewith. One side of the primary of the transformer ll is connected to the terminal 28 and the opposite side is connected to a terminal ll through which the transformer II is connected to the other side of 2,273,811 the circuit. An adjustable resistance 44 having an adjusting knob 45 at the front of the panel I is placed in series with one leg of the primary of the transformer 4| for a purpose to be hereinafter explained. The opposite ends of the main operating winding l9 are led to terminals 46 and The turn 38 is connected through the resistor 42 to the secondary of the transformer 4| as previously described. The contactor is here indicated generally by the reference numeral 54 and the primary of the transformer 4| is connected from the load side of the contactor 54 through the adjustable resistance 44 to the opposite line 52.

An impedance 55 is connected in parallel with the primary of the transformer 4|. Instead of the impedance 55 a transformer might be used having a high leakage reactance to secure the same result. If the leakage reactance of the transformer were made adjustable by varying an I air gap in the magnetic circuit, it would be possible by this method to vary the phase displacement between the secondary current flowing through the turn 38 and the supply. The load device in this figure has been indicated as a welding circuit, including the welding transformer 55, to whose primary the load side of the contactor and the opposite line are connected and to whose secondary are connected welding electrodes indicated diagrammatically at 51.

The operation of the switch so far described is as follows:

When the operating coil i9 is energized, the armature 23 will be attracted thereto and the operating member 22 will rotate about its knife edge pivot 29 on the support 2|. This will bring the movable contact 3i into engagement with stationary contact 4 and will cause the operating member 22 to be moved forwardly relative to the contact finger to stress the compression spring 26 and thus place a resilient bias upon the contact finger which maintains the contact pressure. Upon de-energization of the operating coil l9, and leaving out for the moment the operation of the coil formed by the turn 38, the armature will be released and will move toward its separated position under theaction of the springs 34 and the contact pressure spring 26, as well as by the force of gravity. When operating member 22 reengages the contact finger 25, the contact 3| will separate from the stationary contact 4 and continued movement of the contact and operating member will be effected through the action of gravity and the biasing springs 34. The current through the contactor flows from the terminal I2 through blowout coil contact post 2. contact holder 5, contact 4, contact 3|, contact finger 25 and flexible lead 35 to the terminal 36. Passage of current through the blowout coil creates a fiux within the blowout magnet 8 whose pole faces are spaced at opposite sides of the cooperating contacts and the field between the pole faces tends to blow out any are which might be formed between the contacts.

In the operation so far described, the switch has been of ordinary conventional function; however, now taking into consideration the action of the auxiliary holding coil formed by the turn of conductors 38, a local field is produced by this coil or turn between the cooperating pole faces on the armature 23 and stationary field magnet |4. This local field does not extend around the full magnetic path through the armature and field magnet, but is strictly a local field embracing only the magnetic circuit formed immediately adjacent the coil and through the pole faces. This field will be strong enough to hold the armature in place while thefield has an appreciable value; but, when the field approaches its zero value, it will release the armature and permit it to move forwardly with the operating member 22. The local magnetic circuit formed at the upper pole faces has no appreciable air gap, so that the slightest separation of the armature from the field magnet introduces a large reluctance into this local magnetic circuit; therefore, as the flux produced by the coil or turn 38 tends to build up in thereverse direction, it will not be sufficiently strong to pull the armature back into place, but the armature will continue to move forwardly into its released position. Since the coil is energized from the same source as supplies the welding contactor, and since the coil produces a sufilcient local flux to prevent separation of the armature until the flux produces its zero value, it is-apparent that the armature will always start to separate at a definite point on the supply voltage wave, regardless of the point in this wave at which the main operating coil i9 is 'de energized. So far, therefore,

we have the initial separation of the armature 23 from the field magnet i8 definitely synchronized with the supply voltage.

After the armature separates from the field magnet, it and the operating member 22 must move forward some distance before the operating member engages the contact finger 25 to cause the contact iii to separate from contact 4. The time interval between initial separation of the armature from the field magnet and initial separation of the contacts will be referred to hereinafter as the time constant of the contactor. From the point on the voltage wave at which the armature starts to separate and the time constant of the contactor, it is apparent that we have a definite point on the voltage wave at which the contacts start separating and the circuit is interrupted. The final result which it is desired to synchronize with the supply voltage or current waves is, of course, the initial sepcration of the contacts. Assuming a constant time constant for the contactor, the point of initial separation of the contacts may be shifted along the supply waves by varying the value of the resistance 44 in the primary of the transformer 4| as will be explained hereinafter with respect to the simplified vector diagram of Figure 5. However, if the point of separation of the armature is not made adjustable, or if the limiting values of the resistor 44 do not give the desired result, then the time constant of the contactor can be changed to vary the point on the wave at which the contacts separate. Th s can be done in several ways. The springs 26 can be adjusted by means of the s ud 27 to have a greater or lesser tension. and hence, increase and lessen the speed of dropout of the operator 22, or, of course, these springs may be entirely replaced with springs of different strengths.

Also, the biasing springs 34 may be adjusted to increase or decrease the spring bias, tending to move the operator 22, and these springs also could, of course, be entirely replaced. Also, the gap between the contact finger 25 and the operator 22 in the ON position of the switch can be increased or decreased by the addition or removal of the shims I which determine the position of the stationary contact 4. By any one of these mechanical adjustments, it is apparent that the time constant of the contactor is changed and by proper selection of these me chanical adjustments the point of opening of the contacts can be shifted along the supply waves with respect to the point of initial opening of the armature 23.

With the switch, according to the present invention, connected as diagrammatically shown in Figure 4, the synchronization of contact opening from the determining of the point of armature unsealing and the time constant of the switch or contactor will really synchronize the opening of the contacts with the supply voltage wave. However, if a substantially uniform power factor is present in the load, this will also mean a synchronization or contact opening with the current wave. As ordinary loads will have a somewhat constant power factor for a particular class of work, it is possible to adjust either the time constant or the point of unsealing of the armature for this average of relatively constant power factor, and then the opening of the contacts will be substantially synchronous with the current wave to open thecircuit at substantially the same point on the current wave. As some half cycle with attendant arcing andtime error.

Figure 5 shows a simplified vector diagram in which V1. indicates the line voltage across the line conductors "and 52. Vrindicates the voltage applied to the primary of the transformer I. Is indicates the secondary current flowing through the auxiliary coil formed by conductor ,Il. Ir. indicates total current flowing through the circuit which includes the transformer 4i and impedance 5! in parallel with each other and in series with the variable resistor 44. The dotted line vector positions, IL, I's, V's, represent the relative positions of these variables when the resistance 44 is lowered in value. It is readily apparent that such lowering lessens the resistance drop through the variable resistor and, hence, increases Vr slightly and moves it closer to the base vector Vr. representing the line voltage into the position shown as V's. This also results in rotating the secondary voltage vector Is into the position I's which has changed, therefore, its position with respect to the reference voltage vector Vs, the line voltage. This secondary current Is is flowing through the conductor I. and is thus producing the auxiliary flux which holds the armature in place until its value approaches zero; hence, the rotation of this current vector with respect .to the line voltage also rotates the auxiliary flux vector with respect to the line voltage and changes the point on the line voltage wave at which the armature unseals. Therefore. it is apparent that adjustment of the resistor 44 will vary the point on 28 unseals and. assuming that the time constant of the contactor or switch is not chsngedwill is move the point of opening of the contacts and breaking of the circuit along the-supply voltage wave. Hence, by variation of resistor 44, it is possible to select the point on the voltage wave at which the contacts are separated. Assuming a constant or average power factor this will also determine the point on the supply current wave at which the contacts will separate.

The variations attainable by this adjustment are, of course, limited and, for very large variations in the point at which the contacts separate, it may become desirable to change the time constant of the contactor or switch, as previously described, by one or more of the mechanical adjustments.

Figure 7 has been added to the drawings to indicate the relative operationof the main operating coil l9 and of the auxiliary coil 38. A small air gap is usually maintained at one of the pole faces of the magnetic circuit, in this case the lower, angular pole face, so that the main magnetic circuit will not be sealed. The upper pole faces will be permitted to seal so that the auxiliary local magnetic path for the auxiliary coil 38 will have very low reluctance while the main magnetic circuit will have an appreciable reluctance. This means that a very slight unsealing of the upper cooperating pole faces of the armature and field magnet will reduce the pull exerted by the auxiliary coil to an inappreciable value.

This illustrates why, when once the armature has started to drop out, it will not be again pulled in as the flux produced by the auxiliary coil builds up in the reverse direction. The pull curve of Figure 7 also illustrates that the main operating coil has an appreciable pull even when the operating stroke of the operator 22 or the air gap is quite large so that the main operating coil may function to pull the armature into its energized position.

Figure 6 illustrates an alternative method of energizing the auxiliary coil 38 of the contactor or switch. Here, the main operating coil I! of the contactor 54 is operated in a similar manner from the switch 53, being energized between the lines ii and 52. The'auxiliary coil 38 may have the same limiting resistor 42, but, instead of the potential transformer, parallel inductance, and series resistance previously described, the coil may be energized from a series transformer indicated at 58. This manner of energization and operation has one great advantage, inasmuch as it synchronizes the separation of the contacts with respect to the current wave directly and maintains its synchronization independent of power factor, whereas the previous system synchronizes with respect to the voltage wave and maintains its current synchronization only with respect to an average power factor. One disadvantage of the series transformer energizetion of Figure 6 is the possibility of so large a current flowing through the auxiliary coil as to always hold the armature in place; or, in other words, that this pull, even as the armature starts to separate, would build up quickly enough to pull the armature back into place. This may perhaps be substantially obviated by selecting an iron circuit for the current transformer which would saturate before a dangerous point is reached. A second. disadvantage of this form might be that the contactor would not be quiet unless a load were placed on it, or unless some provision, such as a shading coil, were used; however, where large variations in power factor could be expected in the loads to be controlled and it is desired to synchronize with the load current, the current transformer energlzation might be preferred. It is apparent that with respect to the current transformer energization of Figure 6, initial adjustment of the time constant of the contactor would be required to secure synchronization and that this would be maintained regardless of load current power factor. Wearing of contacts would, of course, change the time constant of the contactor and readjustment might be necessary over periods of time. It is also possible that variation of an air gap in the iron circuit of the current transformer could be used to secure a limited adjustment of the phase displacement of the secondary current to secure the initial synchronization.

Figure 8 illustrates one arrangement by which two series connected single pole contactors could be synchronized. This employs the contactor 54 in the one line and a second contactor 54 in the leg of the supply, with their operating coils l9 and is being controlled by the switch 53. Auxiliary coils 38 and 38 may be provided with the limiting resistor 42 as above, and both fed from the transformer 4| having the impedance 55 in parallel with the primary and the series variable resistor 44. With this arrangement, it is apparent that both armatures will start to unseal at the same point, as determined either by the values of the auxiliary circuit or by variation in the resistor 44 and that the time constants of the two contactors will have to be adjusted to be the same in order to ensure opening of both sets of contacts at substantially the same point with respect to the reference wave. This figure illustrates the manner in which the two contactors could be synchronized using a single auxiliary circuit, although it is obvious that the same result could be produced by duplicating the system of Figure 4 in each leg of the lines ;5i and 52. While this would require duplication of auxiliary equipment, it might be desired due to ease of ensuring exact synchronization of both contactors by means of the relatively fine adjustment of the resistor 44 rather than attempting to secure identical time constants as would be necessary with the system of Figure 8;

It is, of course, also obvious that the synchronized opening of two and three phase circuits could be effected by using three separate single pole'contactors and duplicating in each phase the equipment and connections of the system of Figure 4. The primaries of the auxiliary circuits of the two or three phase system could be connected across any phase with adjustment of individual time constants to secure individual synchronized interruption in the individual phases; or, even in the two and three phase cases the separate single pole contactors in each phase could be fed from a single transformer if adjustment was made in the individual secondaries to the individual auxiliary coils or by individual adjustment of the time constants of the contactors, it being understood that in any case either the points of the unsealing of the individual armatures or the time constants of the individual contactors could be adjusted, or both; in order to secure the separation of contacts at the desired point on the supply Wave.

While applicants invention has been specifically illustrated in connection with a normally open switch in whichdeenergization of the main operating coil produces opening of the contacts and in which the point of separation of the contacts is synchronized, it is readily apparent that iii) if the switch be of the normally closed type in which de-energization of the main operating coil will produce closing of the contacts, applicants invention may be readily applied thereto as well to produce synchronized closing of the contacts; or, in other words, closing of the contacts at the same predetermined point on the supply wave.

The terms sinusoidal form and sinusoidal wave, as used in the appended claims, is intended to cover any alternating current voltage or current whether the wave form is pure sinusoidal or quite irregular in shape, it being understood that in the ordinary practical application of the invention the wave form will quite likely be irregular rather than of true sinusoidal shape. The term sinusoidal has been used in the claims for ease of expression and, as here used, is intended to cover any alternating current voltage or current wave form regardless of shape.

While certain preferred embodiments of the invention have been specifically disclosed, it is understood that the invention is not limited thereto as many variations will be readily apparent to those skilled in the art and the invention is to be given its broadest possible interpretation within the terms of the following claims.

What is claimed is:

1. An electric switch comprising separable contacts, operating means for effecting engagement and disengagement of said contacts to perform the switching-operation, electromagnetic holding means for said contacts including an armature member and a coil energized in synchronization with the supply wave; the flux produced by said coil being sufficient to hold said armature closed until the instantaneous value of the flux is substantially zero, but insufficient to pull the armature back into engagment as the flux builds up in the opposite direction, said armature being connected to maintain said contacts closed while it is attracted, whereby, regardless of the point of actuation of the operating means, the armature will not move to initiate opening of the contacts except at a definite point on the supply wave, and means for adjustably varying the phase displacement between the reference supply wave and the energization wave of the coil to move the point at which the contacts disengage along the supply wave.

2. An electric switch comprising separable contacts, operating means for effecting engagement and disengagement of said contacts to perform the switching operation, means releasable to effect disengagement of the contacts a time interval thereafter, said main operating means effecting release of said releasable means to eifect disengagement of the contacts, auxiliary holding means for said releasable means maintaining it in retained position after release by said main operating means until a definite point on a reference sinusoidal 'wave is reached, and means for adjustably varying the time interval between final release of said releasable means and the disengagement of said contacts to vary the point upon the reference sinusoidal wave at which the disengagement of the contacts occurs 3. In an electromagnetically operated electric switch, relatively movable contacts, a stationary field magnet structure, a main energizing coil for said field magnet, an armature attracted to I said field magnet to effect engagement of said contacts and movable away from said field magnet upon de-energization of said operating coil to effect disengagement of the contacts a time interval after initial movement away from said field magnet, an auxiliary coil, and means energizing said auxiliary coil independently of the operating coil by a current of sinusoidal form and producing a fiux sufilcient to hold the armature in engagement with the field magnet until the flux has an instantaneous value of substantially zero but insufilcient to pull the armature back into engagement as it builds up in the reverse direction after release of the armature, whereby actual released movement of the armature is synchronized with respect to the sinusoidal wave.

4. In an electromagnetically operated electric switch, relatively movable contacts, a stationary field magnet structure, a main energizing coil for said field magnet, an armature attracted to said field magnet to effect engagement of said contacts and movable away from said field magnet upon de-energization of said operating coil to effect disengagement of the contacts a ,time interval after initial movement away from said field magnet, an auxiliary coil, means energizing said auxiliary coil independently of the operating coil by a current 01' sinusoidal form and producing a fiux sufilcient to hold the armature in engagement with the field magnet until the flux has an instantaneous value of substantially zero but insuificient to pull the armature back into engagement as it builds up in the reverse direction after release of the armature, whereby actual released movement of the armature is synchronized with respect to the sinusoidal wave, and means for adjustably varying the time interval between actual release of the armature and'disengagement the contacts to vary the point upon the sinusoidal wave at which the contacts actually disengage.

5. In an electromagnetically operated electric switch, relatively movable contacts, a stationary field magnet structure, a main energizing coil Ior said field magnet, an armature attracted to said field magnet to eflect engagement of said contacts and movable away from said field magnet upon de-energization of said operating coil toefiect disengagement of the contacts, an auxilhry coil, means energizing said auxiliary coil independently of the operating coil by a current of sinusoidal form in synchronization with the supply controlled by said separable contacts and producing a fiux sufilcient to hold the armature in engagement with the field magnet until the fiux has an instantaneous value of substantially zero but insufilcient to pull the armature back into engagement as it builds up in the reverse direction after release of the armature, whereby actual released movement of the armature is synchronixed with respect to the auxiliary energization" and supply waves, and means for adjustably varying the phase displacement between said auxiliary cnergizstion wave and the supply wave to vary the point on the supply wave at which the contacts are disengaged.

6. In an electromagnetically operated electric switch, relatively movable contacts, a stationary field magnet structure, a main energizing coil for said field magnet, an armature attracted to said field magnet to efiect engagement of said contacts and movable away from said field magnet upon de-energization of said operating coil to elect disengagement oi the contacts a time interval after initial movement away from said field magnet, an auxiliary coil, means energizing said auxiliary coil independently of the operating coil by a current of sinusoidal form in synchronisation with the supply controlled by said separable contacts and producing a flux sufiicient to hold the armature in engagement with the field magnet until the flux has an instantaneous value of substantially zero but insuillcient to pull the armature back into engagement as it builds up in the reverse direction after release of the armature, whereby actual released movement of the armature is synchronized with respect to the auxiliary energization and supply waves, and means for adjustably varying the time interval between initial movement of the armature and disengagement of the contacts to vary the point on the supplywave at which the contacts disengage.

7. In an electromagnetically operated electric switch, relatively movable contacts, a stationary field magnet structure, a main energizing coil for said field magnet, an armature attracted to said field magnet upon energization of said operating coil to eileot engagement of the contacts and movable away from said field magnet upon de-energization of said coil to effect disengagement of the contacts, an auxiliary coil, means energizing said auxiliary coil independently of the operating coil by a current of sinusoidal form in synchronization with the supply controlled by said separable contacts and producing a fiux sumcient to hold the armature in-engagement with the field magnet until the flux has an instantaneous value of substantially zero but insufiilcient to pull the armature back into engagement as it builds up in the reverse direction after release of the armature, whereby actual released movement of the armature is synchronized with respect to the auxiliary. energization and supply waves, and means for adjustably varying the phase displacement between the auxiliary energization wave and the supply wave to effect disengagement of the contacts when the supply current has an instantaneous value of substantially zero.

8. In an electromagnetically operated electric switch, relatively movable contacts, a stationary field magnet structure, a main energizing coil for said field magnet, an armature attracted to said field magnet to eiIect engagement of said contacts and movable away from said field magnet upon de-energization of said operating coil to eilect disengagement oi' the contacts, a time interval after initial movement away from said field magnet, an auxiliary coil, means energizing said auxiliary coil independently of the operating coil by a current of sinusoidal form in synchronization with the supply controlled by said separable contacts and producing a flux sumcient to hold the armature in engagement with the field magnet until the fiux has an instantaneous value of substantiallyzero but insumcient to pull the armature back into engagement as it builds up in the reverse direction after release of the armature, whereby actual released movement 0! the armature is synchronized with respect to the auxiliary energization and supply waves, and means for adjustably varying the time interval between initial movement of the armature and disengagement oi the contacts to efi'ect the disengagement oi the contacts when the supply current has an instantaneous value of substantially zero.

9. In an electromagnetically operated electric switch, cooperating contacts, electromagnetic operating means for said contacts including stationary and movable magnetic portions having cooperating laces, a main operating coil ior eneradjacent one of said faces, and means independently energizing said auxiliary coil and producing a flux sufiicient to hold said faces in engagement until the instantaneous value thereof is substantially zero, said fiux being insufiicient to pull the movable magnetic portion back into engagement as it builds up in the opposite direction after the faces have separated.

10. In an electromagnetically operated electric switch, stationary and movable contacts, a stationary field magnet, an energizing coil for said field magnet, an armature cooperating with said field magnet and operatively connected to said movable contact to effect switching operation thereof, an auxiliary coil disposed adjacent one of the cooperating faces of said armature and field magnet and adapted to create a local magnetic field including only the magnetic material immediately adjacent said cooperating faces, and means for energizing said auxiliary coil with a sinusoidal current of the same frequency and bearing a fixed phase displacement with respect to the wave form of the supply controlled by said contacts, said. auxiliary coil remaining energized after de-energization of said main coil and re- -taining said armature in its attracted position until said local magnetic field has an instantaneous value of substantially zero.

11. In an electromagnetically operated electric switch, stationary and movable contacts, a stationary field magnet, an energizing coil for said field magnet, an armature cooperating with said field magnet and operatively connected to said movable contact to effect movement thereof to perform the switching operation, an auxiliary coil adjacent to and enclosing only a portion of one of the cooperating faces between said armature and field magnet, whereby a local magnetic path is established for said coil including said faces and through which the flux is in opposite directions in the embraced and unembraced portions of the faces, means for energizing said auxiliary coil separately from said field magnet ener gizing coil and maintaining it energized after deenergization of said field magnet energizing coil, the local flux produced by said auxiliary coil holding said armature in attracted position until it has an instantaneous value of substantially zero and being incapable of pulling the armature back into attracted position as the fiux builds up in the opposite direction after initial release of the armature, whereby the release of the armature will be synchronized with respect to the wave form of the current in the auxiliary coil irrespective of the point at which the field magnet energizing coil is deenergized.

12. In an alternating current system, an alternating current supply, a load connectable to said supply, an electric switch including stationary and movable contacts controlling the connection of said load to said supply, a stationary field magnet in said switch, an armature cooperating with 1 said field magnet and connected to move said movable contact to perform the switching operation, an energizing coil for said field magnet con- I trollably connected to said supply, a transformer having its primary winding connected across said supply, and an auxiliary coil for at least a portion of said field magnet energized through the secondary winding of said transformer, the current through said auxiliary coil producing a fiux sufficient to hold the armature in attracted position until the flux has an instantaneous value of substantially zero, but insufficient to pull the armature back into attracted position as the fiux builds up in the opposite direction after initial release of the armature, said auxiliary coil remaining energized after deenergization of said main field magnet energizing coil, whereby release of the armature and movement of th movable contact is synchronized with respect to the wave form of the supply.

13. In an alternating current system, an alternating current supply, a load connectable to said supply, an electric switch including stationary and movable contacts controlling the connection of said load to said supply, a stationary field magnet in said switch, an armature cooperating with said field magnet and connected to move said movable contact to perform the switching operation, an energizing coil for said field magnet controllably connected to said supply, a transformer having its primary winding connected across said supply, an auxiliary coil for at least a portion of said field magnet energized through the secondary winding of said transformer, the current through said auxiliary coil producing a flux sufficient to hold the armature in attracted position until the flux has an instantaneous value of substantially zero, but insufficient to pull the armature back into attracted position as the flux builds .up in the opposite direction after initial release of the armature, said auxiliary coil remaining energized after de-energization of said main field magnet energizing coil, whereby release of the armature and movement of the movable contact is synchronized with respect to the wave form of the supply, and an adjustable resistor in series with the primary winding of the transformer energizing said auxiliary coil, adjustment of said resistor varying the phase displacement between the current in the auxiliary coil and the supply I voltage and current and thereby varying the point on the supply wave at which the contact movement takes place.

14. In an alternating current system, an alternating current supply, a load connectable to said supply, an electric switch including stationary and movable contacts controlling the connection of said load to said supply, a stationary field magnet in said switch, an armature cooperating with said field magnet and connected to move said movable contact to perform the switching operation, an energizing coil for said field magnet controllably connected to said supply, a transformer having its primary winding connected across said supply, an auxiliary coil for at least a portion of said field magnet energized through the secondary winding of said transformer, the current through said auxiliary coil producing a flux sufficient to hold the armature in attracted position until the flux has an instantaneous value of substantially zero, but insufficient to pull the armature back into attracted position as the flux builds up in the opposite direction after initial release of the armature, said auxiliary coil remaining energized after de-energization of said main field magnet energizing coil, whereby release of the armature and movement of the movable contact is synchronized with respect to the wave form of the supply, an inductance connected in parallel with the primary winding of said transformer, and an adjustable resistor connected in series with the parallel circuit formed by said inductance and transformer primary. variation in said resistor value changing the phase displacement of the auxiliary coil current with respect to the supply voltage and current, and thereby varying the point on the supply wave at which contact movement occurs.

15. In an alternating current system, an alternating current supply, a load connectable to said supply, an electric switch including stationary and movable contacts controlling the connection of said load to said supply, a stationary field magnet in said switch, an armature cooperating with said field magnet and connected to move said movable contact to perform the switching operation, an energizing coil for Said field magnet controllably connected to said supply, a current transformer having its primary connected in series with said supply, and an auxiliary coil for at least a portion of said field magnet energized by the secondary of said current transformer and producing a flux sufilcient to hold said armature in attracted position until the fiux has an instantaneous value oi substantially zero, but insufficient to pull the armature back into attracted position as it builds up in reverse direction after initial release of the armature, whereby the release of the armature and movement of the movable contact is synchronized with respect to the'supply current.

16. In an alternating current system, an alternating current supply, a load connectable to said supply, an electric switch including stationary and movable contacts controlling the connection of said load to said supply, a stationary field magnet in said switch,'an armature cooperating with said field magnet and connected to move said movable contact to perform the switching operation, an energizing coil for said field magnet controllably connected to said supply, a current transformer having its primary connection in series with said supply, an auxiliary coil for at least a portion of said field magnet energized by the secondary of current transformer and producing a flux sufilcient to hold said armature in attracted position until the fiux has an instantaneous value of substantially zero, but insufficient to pull the armature back into attracted position as it builds up in reverse direction after initial release of the armature, whereby the release of the armature and movement of the movable contact is synchronized with respect to the supply current, and means for varying the time interval between movement of the movable contact and the release of the armature to vary the point on the supply current wave at which the movable contact is actuated.

17. An electric switch comprising relatively movable contacts, a stationary field magnet structure, a main energizing coil for said field magnet, an armature adapted to be attracted to and released from said field magnet to effect the switching operation, said field magnet and armature including cooperating pole faces engaging in the attracted position of the armature, and an auxiliary coil recessed into at least one of said faces and having'terminal portions providing for the independent energization thereof, said auxiliary coil establishing a local fiux passing through said cooperating faces, and meansfor energizing said auxiliary coil with a current of suificient value to produce a flux sumcient to hold the faces in engagement until the instantaneous value thereof is substantially zero, initial separation of said faces introducing a large reluctance into the local magnetic path of the auxiliary coil, whereby the flux will be insuificient to pull the armature back into engagement with the field magnet afterits initial separation therefrom.

18. An electric switch comprising relatively movable contacts, a stationary field magnet structure, a main energizing coil for said field magnet, an armature adapted to be attracted to and released from said field magnet to eifect the switching operation, said field magnet and armature including cooperating pole faces engaging in the attracted position of the armature, and an auxiliary coil recessed into at least one of said faces and having terminal portions providing for the independent energization thereof, said auxiliary coil establishing a local fiux passing through said cooperating faces, and means for energizing said auxiliary coil with a current out of phase with the current in the main operating coil and of sufilcient value to produce a local fiux which will hold the faces in engagement until the value thereof produces zero, whereby the separation of faces will be synchronized with the energization of the auxiliary coil and the auxiliary coil will further function to maintain the pole faces in engagement during alternation of the fiux in the main magnet to prevent chattering of the magnetic parts.

19. In an electromagnetically operated electric switch, a stationary contact, a movable contact, a stationary field magnet structure, a main energizing coil for said field magnet, an armature adapted to be attracted to and released from said field magnet in response to energization and deenergization of said coil, an operative connection between said armature and movable contact, said field magnet and armature including cooperating pole faces engaging in the attracted position of the armature. recesses in at least one of said pole faces and an auxiliary coil disposed in said recesses and having terminal portions providing for energization thereof independently of the main operating coil, and means for energizing said auxiliary coil with a current of sumcient value to produce a local fiux passing through the cooperating faces of suificient intensity to maintain the faces in engagement until the-value of the flux produces zero, whereby after deenergization of the main operating coil, the'armature will not initiate its movement until the local flux of said auxiliary coil produces its zero value.

20. An electric switch comprising relatively movable contacts, a stationary field magnet structure, a main energizing coil for said field magnet, an armature adapted to be attracted to and released from said field magnet to effect the switching operation, said field magnet and arma ture including cooperating pole faces engaging in the attracted position of the armature, and an auxiliary coil recessed into at leastsone of said faces and having terminal portions providing for the independent energization thereof, said auxiliary coil establishing a local flux passing through said cooperating faces, and means for energizing said auxiliary coil from the supply controlled by the switch to establish a local fiux maintaining the faces in engagement after opening of the main energizing coil until the local flux value produces zero, and means for varyingv the phase angle of the current in said auxiliary coil with respect to the supply so as to vary the point on the supply wave at which the armature unseals.

ERNEST G. ANGER. 

